Operation Thunderstorm

What is a thunderstorm? Nobody knows exactly, because science has never thoroughly dissected one.

Last week U.S. scientists were busy at the long-neglected job. Using one of the most elaborate collections of paraphernalia ever assembled--planes, radar, cameras, raindrop measurers, recording devices in great variety--the Army Air Forces, Navy and U.S. Weather Bureau had launched a project to find out all that man can know about a storm, from its fleecy birth to crescendo climax. Because thunderstorms are flying's greatest hazard, the investigators hope their study will develop reliable methods of recognizing and avoiding dangerous types of cloud.

At the A.A.F.'s Pinecastle Field, near Orlando, Fla., where afternoon thunderheads are a daily midsummer occurrence, five Black Widow planes take off each day to fly in the hazardous clouds. Guided by a radar control station called Ivy, and attended by a host of balloon-borne instruments, they measure air turbulence, the velocity of up-and downdrafts, temperature, pressure, humidity, 'cloud heights, the size of ice particles. Though no planes have been lost, they have taken a fearful buffeting; one pilot, whose instruments were knocked out by lightning, found when he fought his way out of the storm that he was flying upside down.

The stars of the show are a pair of storm-tossed gliders which, riding like leaves on the violent air gusts, have turned up much new information about a storm's inner currents. Some facts already learned:

A thunderstorm begins with a tremendous uprush of air, which rises to 16,000 feet or more. As the storm mounts in intensity, the winds reverse themselves, blow downward. Heavy rain is no measure of a storm's violence; the wildest gusts often grow in rainless thunderheads or even in harmless looking clouds.

Between 6,000 and 11,000 feet, a thunderhead is a maelstrom of vertical drafts which can toss a plane up or down at the rate of 4,500 feet a minute. Above 14,000 feet, the rain turns to ice and the storm becomes a white blizzard.

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